1. Field of the Invention
The present invention relates to a method for clock rate conversion of digitized television signals for generating a television signal having a prescribed processing clock rate given a fixed scan clock rate of the coded television signal.
2. Description of the Prior Art
The clock rates for sampling an analog television signal and the clock rate for further processing or, respectively, transmission of the digitized television signal are rigidly prescribed in the transmission of black-and-white and color television signals. These clock rates frequently do not coincide and likewise do not have a rational relationship. A clock rate conversion by which television signals having prescribed processing clock rates are acquired must then occur. These television signals can be supplied to a corresponding coder for further data reduction by way of a DPCM method.
What is meant by television signals are both the luminance signals and the chrominance signals. At present, the method is of interest particularly for luminance signals.
Various methods for clock rate conversion are known. A data stream having a first clock frequency is thereby converted into a second data stream having a different clock frequency. Such a method is disclosed in the periodical "Frequenz", Vol. 36, No. 10, 1982, pp. 275-279. To this end, a time-invariant, linear filter is employed to which the digitized signal values are supplied with the first clock frequency and which emits the digitized signals with a second clock frequency at the output via a summer element. This conversion method is co-employed in the present invention. The method, however, presumes that the relationship of the second clock rate to the first clock rate yields a rational value. Given the processing clock rate that are currently standard, however, this is usually not the case.